The use of conducting wires to carry electrical power is well known, as is the fact that a current passing through a conductor generates an external magnetic field around the conductor.
In many environments, magnetic fields of this type are undesirable, such as under high-power transmission lines or in power cords in certain locations, or generally any area where people or animals are exposed to high magnetic fields. For example, power supplies for pacemakers implanted in a person's body transmit power inside the person's body, and a magnetic field there is undesirable. As another example, in the context of hybrid cars, power is supplied via cables within the body of the car, usually as relatively high-amperage, high-voltage alternating current, e.g., 360 volt AC, which can produce undesirable exposure of people in the car to high magnetic fields.
The prior art reflects some efforts to reduce the effect of a magnetic field around a conductor. For example, shielding methods have also been employed in the prior art using magnetized materials. Shielding to block magnetic fields generally involves application of a coating or surrounding cover that prevents some of the magnetic field around the conductors from extending through it.
Depending on the material used, the coating material can be relatively expensive. Also, it may be vulnerable to damage so that the magnetic field leaks through. Even if intact, there is a degree of magnetism that is not interrupted by the shielding, and that may, depending on the conditions, constitute an unacceptable level of magnetic field around the conductor.